Clinical studies in advanced carcinoma of the head and neck region, Hodgkin's disease and non-Hodgkin's lymphomas, carcinoma of the breast, gastrointestinal cancer, gynecologic malignancies, prostatic cancer and radiation dose rate effects on the hematopoietic system are continued and new studies are planned. Radiological physics research includes: magnetic control of the dose distributions produced by high energy electron beams, calorimetric determination of dosimetric parameters and general medical physics. Laboratory investigations include: experimental radiation therapy of rodent solid tumors, radiation reaction preventive agents and normal tissue response, the response of vascular endothelium to ionizing radiation, NMR detection of hypoxic cells, the influence of the red blood cell concentration of 2,3-diphosphoglycerate on the radiation response of the rat rhabdomyosarcoma R1112. Our investigations also include: enzymatic mechanisms in postreplication repair; study of error-prone DNA repair pathways in mammalian cells, study of herpes virus genome structure, site specific mutagenesis in gene for thymidine kinase of herpes simplex virus; molecular mechanisms of DNA repair in E. coli, hypoxic radiosensitizers: structure-function relations and mechanisms of sensitization and toxicity; analysis of gene function involved in genetic recombination in E. coli; site directed mutagenesis, role of secondary structure in gene regulation; cell proliferation in EMT6 tumors and examination of new agents for altering the radiation response of solid tumors.